Air cooled piston engines rely on the circulation of air around the pistons and other hot parts for cooling. While many applications, such as automobiles, have favored circulating a liquid around the engine for cooling, air cooled engines are still favored in many applications. An air-cooled engine will usually have lower weight, be more compact, and have less mechanical complexity than a similar liquid cooled engine. For this reason, air-cooled engines are still commonly used in smaller vehicles such as motorcycles.
Many motorcycles use air-cooled engines to reduce weight and complexity. In particular, popular motorcycle engines commonly designated as “V-twin” and associated with motorcycles manufactured by Harley-Davidson Motorcycle Company, remain air cooled. While air cooling provides effective heat transfer for the metal engine parts for V-twin type engines, in some conditions, additional cooling provisions may be needed for the engine oil.
In some conditions, such as when the motorcycle is idled and the outside air temperature is relatively high, the oil temperature increases beyond a safe operating temperature. This may result in a loss of needed lubrication properties (e.g., viscosity) and may also cause a loss of oil pressure. As such, external oil coolers are sometimes provided to assist in maintaining safe oil pressure.
Typically, factory and aftermarket oil coolers include a heat exchanger (e.g., a finned radiator) that is designed to mount on the frame directly in front of the engine and behind the front wheel. This location has some advantages, such as shortening the length of oil supply lines and keeping the hot heat exchanger away from the rider's legs. However, the front wheel, fenders, forks, and other bike mounted accessories cause a blockage of some of the airflow that reaches such a radiator. Further, the close proximity to the hot engine may somewhat reduce the effectiveness of the heat exchanger. As a result, this type of oil cooler needs to be sized larger (and thus heavier) than would otherwise be required to account for the airflow blockages and engine heat. Because lower weight provides increased motorcycle performance, an improved, lower weight, oil cooler filter heat exchanger is desirable.